An organic light-emitting diode (OLED) is a light-emitting diode (LED) made of semiconducting organic polymers. These devices promise to be much cheaper to fabricate than inorganic LEDs. Varying amounts of OLEDs can be deposited in arrays on a screen by use of simple “printing” methods to create a graphical color display, for use as television screens, computer displays, portable system screens, and in advertising and information board applications. OLED panels may also be used as lighting devices.
One of the great benefits of an OLED display over the traditional liquid crystal displays found in computer monitors is that OLED displays do not require a backlight in order to function. This means that they draw far less power and can be used with small portable devices, which have mostly made use of monochrome, low-resolution displays, in order to conserve power. This also means that they are able to last for long periods of time on a single battery charge.
There are two main directions in OLED technology. The first OLED technology was developed by Eastman Kodak Company (Rochester, N.Y.) and is usually referred to as “small-molecule” OLED. The production of small-molecule displays requires a vacuum deposition process, which makes the production process expensive and inflexible. A second OLED technology, developed by Cambridge Display Technology (Cambridge, UK), is a polymer-based OLED technology, which is sometimes referred to as PLED technology. Although development of PLED technology lags behind the development of small-molecule OLED technology by several years, it promises some advantages. For example, the organic electroluminescent materials can be applied on the substrate by a technique derived from commercial inkjet printing, which means that PLED displays can be made in a very flexible and inexpensive way.
Producing a multi-color organic display is not an easy task. While the use of inkjet printing techniques for forming PLED displays has found some acceptance in forming displays with larger feature sizes, the technique has, so far, depended on a complex and costly photolithography process for forming the receptacles upon the display substrate. The receptacles, or wells, are structures that are formed upon a substrate into which, in the case of a PLED display, the droplets of polymer solution are collected during an inkjet deposition process. What is needed is a simpler and less costly process for forming receptacles upon a display substrate for use in a subsequent inkjet deposition process that delivers the polymer solvent thereon for completing the display fabrication.
One exemplary method of forming a light-emitting display by use of an inkjet deposition process is found in reference to U.S. Pat. No. 6,767,774, entitled, “Producing Multi-color Stable Light-Emitting Organic Displays.” The '774 patent describes a polymer or organic light-emitting display that may be formed on a substrate by patterning the light-emitting material by use of a screen printing technique. In this way, displays may be formed economically and overcome the difficulties associated with photoprocessing light-emitting materials. A binary optic material may be selectively incorporated into sol gel coatings and coated over light-emitting elements formed from the light-emitting material. A tricolor display may be produced by use of a light-emitting material that produces a single color.
While the '774 patent describes a suitable method of forming a light-emitting display by use of an inkjet deposition process, it makes no mention of providing simpler or more inexpensive ways to form the receptacle structures upon a substrate for use in the inkjet deposition process.
It is therefore an object of the invention to provide a simplified and inexpensive process for forming receptacles upon a display substrate for use in a subsequent inkjet deposition process for forming a large-area PLED/OLED display.
It is another object of this invention to provide a method of using a shadow mask vacuum deposition process for forming receptacles upon a display substrate for use in a subsequent inkjet deposition process.